Modification of the Associations Between Duration of Oral Contraceptive Use and Ovarian, Endometrial, Breast, and Colorectal Cancers.

ABSTRACT: Importance:Although oral contraceptive (OC) use is common, the influence of OC use on carcinogenesis is not fully understood. A recent Agency for Healthcare Research and Quality report identified a need to understand the consistency of OC use and cancer associations across subpopulations, including smokers and obese women. Objective:To determine whether associations between duration of OC use and risk of specific cancers were modified by lifestyle characteristics. Design, Setting, and Participants:The prospective NIH-AARP Diet and Health Study (enrolled 1995-1996, followed until 2011), with population-based recruitment of AARP members in 6 states and 2 metropolitan areas. All analyses included at least 100?000 women who reported OC use at enrollment. We identified 1241 ovarian, 2337 endometrial, 11?114 breast, and 3507 colorectal cancer cases during follow-up. Data analysis was performed between September 2016 and April 2017. Exposures:Duration of OC use (never or <1 year [reference], 1-4, 5-9, or ?10 years). Main Outcomes and Measures:Development of ovarian, endometrial, breast, and colorectal cancers. We examined effect modification by modifiable lifestyle characteristics: cigarette smoking, alcohol consumption, body mass index (BMI), and physical activity. We used Cox models adjusted for age, race, age at menarche, and the modifiers of interest. Results:The analytic population was aged 50 to 71 years (median, 62 years) at enrollment and largely white (91%) and postmenopausal (96%). For ovarian cancer, OC use-associated risk reductions strengthened with duration of use (long-term OC use [?10 years] HR, 0.60; 95% CI, 0.47-0.76; P?

SUBMITTER: Michels KA 

PROVIDER: S-EPMC5885214 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature